Damage Tolerance Behavior of a Nickel-Based Super-alloy GTM718 Under Cold-TURBISTAN Variable Amplitude Loads

In this study, the damage tolerance behavior in terms of fatigue crack propagation behavior of an aero-engine material under a standard variable amplitude load sequence was predicted and compared with experimental results. The constant amplitude (CA) fatigue crack growth rate (FCGR) behavior of GTM718, a nickel-based super-alloy, was determined at various stress ratios R = σmin/σmax ranging from R = 0.1 to 0.7. The empirical fatigue crack growth law was derived from this data in terms of two-parameter crack driving force, ΔK*. Then, the fatigue crack propagation behavior of GTM718 under a standard cold-TURBISTAN variable amplitude load sequence was predicted using cycle-by-cycle approach and using the CA fatigue crack growth law. Also, experimental fatigue crack growth behavior under the same cold-TURBISTAN variable amplitude load sequence was determined and compared with predicted results. A fairly good correlation was observed with predicted and experimental results